It is perfectly normal to have oil on your air filter, as far as mopars design team is concerned. It is a normal part of the ccv system these engines employ. As far as your piston rings are concerned, if your compression tests were all within nop with no considerable variations and it is not burning oil, they are fine and not to be worried about. As for your friends advice on pistons not touching oil, stop taking advice from this friend. The head should not come in contact with oil, that's what the rings are designed for. At 140k you shouldn't really be too concerned with overhauling the block. If you smell oil burning in the exhaust and notice when it isn't cold out that there is still significant "smoke" coming from the tail pipe then it would be something to consider. But, until then, keep calm and keep wheelin'!